美国麻省理工学院分子自组装实验室简介

一九九三年,麻省理工学院发布了十五项二十世纪最后二十五年中麻省理工科学家所取得的重大科学成就,大部分人选的科学家为诺贝尔奖获得者。在这十五项成就中,有两项为美籍华裔科学家所做出的贡献：一项是美籍华裔物理学家、诺贝尔奖获得者丁肇中博士关于物质夸克粒子的发现;另一项则     

ONTOGENETIC VARIATION IN PATTERNS OF PHENOTYPIC INTEGRATION IN THE LABORATORY RAT

I used confirmatory factor analysis to evaluate the ability of causal developmental models to predict observed phenotypic integration in limb and skull measures at five stages of postnatal ontogeny in the laboratory rat. To analyze the dynamics of phenotypic integration, I fit successive age-classes simultaneously to a common model. Growth was the principal developmental explanation of observed phenotypic covariation in the limb and skull. No complex morphogenetic model more adequately reconstructed observed covariance structure. Models that could not be interpreted in embryological terms, coupled with a growth component, provide the best models for observed phenotypic integration. During postnatal growth, some aspects of integration vary in both the skull and limb. The covariance between factors and the proportion of variance unique to each character differ between some sequential age-classes. The factor-pattern is invariant in the limb; however, repatterning in the skull occurs in the interval between eye-opening and weaning. The temporal variation in the structure of covariation suggests that functional interactions among characters may create observed patterns of phenotypic integration. The developmental constraints responsible for evolutionary modification of phenotypes might be equally dynamic and responsive to embryonic functional interactions.     

IMPROVEMENTS IN THE DESIGN OF A LABORATORY CULTURE VESSEL

SUMMARY: The application of a radial mechanical shaft seal, and other improvements to a 2–3 1. capacity culture vessel, are described.     

孕期接触四氯联苯对大鼠母性行为的影响

为评价多氯联苯对人体发育的影响,本研究以大鼠为模型,研究多氯联苯（PCB）对母性行为的影响。将50只同期怀孕的Long-Evans大鼠随机分为5组,在怀孕第7－18天,每天给大鼠肌注四氯联苯或芝麻油。1组、2组,按每kg体重分别注射1mg、20mg2,2′,4,4′－四氯联苯（PCB47）;3组、4组,按每kg体重分别注射0.25mg、1mg3,3′,4,4′－四氯联苯（PCB77）;5组（对照组）注射芝麻油。产仔后的第0、3、6、12、15天分别观察母鼠的筑窝、舔仔、自发叼仔和诱发叼仔、蹲伏和在窝内的时间。结果表明：对照组母鼠在30min的观察中,其窝内时间与幼仔出生后天娄和负相关,而接触PCB的母鼠的窝内时间与幼仔出生天数无相关关系。接触PCB47的母鼠的筑巢、蹲伏、舔仔、自发叼仔行为在幼仔出生后的第0天和6天与对照组有显著差异,而接触PCB77的母鼠仅在第15天与对照组大鼠有区别。在诱导叼仔的实验中,接触PCB77的母鼠的叼仔时间在幼仔出生后的第12天增加。     

GROWTH AND DEMOGRAPHY OF POPULATIONS OF BIOMPHALARIA PFEIFFERI (GASTROPODA, PLANORBIDAE) IN THE LABORATORY

The growth and demography of the freshwater snail Biomphalariapfeifferi, an intermediate host of the parasitic worm Schistosomamansoni in Eastern Zaire, were investigated in the laboratoryunder two conditions of crowding. Both individual and populationgrowth were depressed by crowding. Crowding reduced growth rateand all the variables and parameters related to reproduction(fecundity, instantaneous birth rate, net reproduction rate),but did not affect maximum size, survivorship, instantaneousdeath rate and life expectancy. The mechanism involved in theseeffects is likely to be exploitation competition for especiallyprofitable food items such as diatoms. (Received 10 November 1986;